The invention relates to the field of biocompatible bone fillers and bone conforming materials, and more particularly to a bone filler and bone conforming agent that can be shaped into an implant that remains moldable for some time after being implanted in the body, and a method for using same.
The invention is directed to moldable, post-implantation bone fillers and bone conforming materials that can be formed into an implant that remains moldable for some time after being implanted in the body and a method for using the same. During various surgical procedures, including but not limited to orthognathic surgeries (surgeries of the jaw and related areas), the surgeon will often identify depressions and other deformities in the shape and contour of various bone structures. Indeed, in the field of facial surgeries, one common reason to carry out surgical procedures is to make aesthetic and/or functional improvements to the face. Many times these surgeries require changing the size, shape, and/or position of underlying bone structure (e.g. shortening, lengthening, or widening the jaw, augmenting the chin, etc). Because the underlying bone structure of interest (which is covered with muscle, fat, skin and other tissues) has a great influence in determining the exterior contours and appearance of the body, the ability to easily correct defects and deficiencies in the post-operative bone structure would be very helpful.
Presently, there are several methods surgeons employ to accomplish this, including using implants made of silicone, various metals (such as stainless steel and other materials), hydroxyapatite and other material. There are sometimes infection problems associated with implants made of materials that are not completely biocompatible, such as silicone implants. Hydroxyapatite, Ca10(PO4)6(OH)2, is similar in property to coral, which is remarkably close in chemical composition and structure to human bone. In fact, human bone will grow in to the porous structure of the implant material and can sometimes even entirely replace the implanted hydroxyapatite. Other common implant materials include highly processed bone (from animal or cadaver sources, U.S. Pat. No. 5,501,706), calcium phosphate cements (U.S. Pat. No. 5,697,981), physiological serums containing hydroxyapatite (U.S. Pat. No. 5,591,232) and sintered apatite bodies and composites (U.S. Pat. No. 4,503,157).
Hydroxyapatite is typically provided in the form of microspherical particles that can be implanted to a site that needs augmentation, for example, by injection via a syringe-like device. Since the microspheres are like small ball bearings, they tend to drift, move or xe2x80x9cflowxe2x80x9d away from the implantation site after being implanted. Thus, little control can be exercised over the results. Eventually, the hydroxyapatite microspheres will stabilize (although as explained above, not always where the surgeon wants them to be concentrated). In other cases, hydroxyapatite is provided in solid blocks that can be machined in to a particular shape, and then inserted in the desired location adjacent to the bone undergoing repair, replacement or modification. The solid block sources must be shaped to fit the specific requirements of the repaired, replaced or modified bone and are not easily fabricated to conform to the desired bone shape. Typically, such solid blocks of pure hydroxyapatite are appropriate for use in expanding jaws and the like where a solid structure without any moldability is desired.
While calcium phosphate cements are known that harden in-situ or that harden and then are shaped in to a pre-formed object useful in bone repair, there remains a need for a moldable, post-implantable bone filler and bone conforming material and a method for using such a bone filler and bone conforming material.
The invention provides a moldable, post-implantable bone conforming material and a method for using the bone filler. The bone conforming material comprises an apatite material and a fibrous material, such as fibrous proteins (e.g. collagen) mixed with enough physiological fluid added to form a paste. The bone filler and the method of using the bone material permits a surgeon to form implants of desired shapes and sizes outside of the body, implant the bone conforming material against the bone, close the surgical site, and continue to be able to adjust or modify the contours of the patient body in the areas with the bone conforming material for a period of time by applying pressure to the skin, muscle, and other tissue overlaying the bone conforming material implant to thereby mold or shape the implanted bone conforming material. The time period during which the bone conforming material can continue to be molded is about eight weeks or longer.
There are tremendous advantages to the bone conforming material of the present invention. First, a surgeon can mix together a moldable bone conforming material and pre-shape the bone conforming material into a desired shape prior to implantation. The surgeon will then dry the molded bone conforming material, thereby curing it to a hardened shape and state, preferably by placing it under a heat lamp, in a heated oven, in a dehydration unit under warm/hot air flow or a dessicant, or by other suitable curing means. In its hardened state, it retains its shape and state. It is also possible to rely on air drying solely, which takes considerably more time, as compared to drying using a heating unit. After the hardened implant is positioned in a desired place in the body against a bone structure, it becomes saturated with blood and other physiological fluids and softens somewhat like a hardened sponge softens when saturated. In its softened state, it can be molded further at the implantation site to more closely conform to the bone and continue being shaped as required. However, even when it is saturated and softens, it will not crumble or break up, and remains moldable. After the surgery, the surgeon will close the surgery site over the implant. The surgical site will remain inflamed and swollen for some time, generally for at least several days to several weeks. For this reason, it is not always apparent to the doctor at the time of implantation how best to shape the bone conforming material to the bone. The ability to mold the bone conforming material, after the swelling has gone down, allows the surgeon to carry out further shaping of the bone conforming material to achieve improved aesthetic results. In addition, pre-curing the bone conforming material prevents the inherent drift of bone material associated with microspherical bone conforming material materials and methods.